Generate yaml files with PV fields

[kabanaty]

Is your feature request related to a problem? Please describe.
Many wire scanner values are reported back through fields of the MOTR record, e.g. MOTR.VELO, MOTR.RBV, MOTR.STOP, etc. It is currently impossible to add a PV field as a PV to the yaml file.

Describe the solution you'd like
Introduce a method to include PV fields as controls information PVs when generating yaml files.